AB0868 IMMUNE CHECKPOINT INHIBITOR-ASSOCIATED MYOPATHY
Authors: M. Pavía Pascual, N. De La Torre Rubio, M. Machattou, P. Navarro Palomo, C. Navarro Joven, M. Alonso de Francisco, C. Barbadillo Mateos, C. Merino Argumánez, H. Godoy, M. Fernandez Castro, B. Garcia-Magallon, J. Sanz, L. F. De Villa, J. L. Andréu Sánchez, J. Campos Esteban
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> In recent decades, immunotherapy has changed the management and prognosis of cancer patients. Immune checkpoint inhibitors, such as those targeting PD-1 and PD-L1, are used for some types of cancer; however, their use has been associated with the appearance of immune-mediated adverse events. Among these, those related to the field of rheumatology are relatively frequent, joint involvement being the most common, followed by muscle involvement (myalgias 4%, myositis 1%). <h3>Objectives</h3> To describe oncologic patients who developed immune checkpoint inhibitors- related myositis. <h3>Methods</h3> All patients from the oncology department of a tertiary hospital, referred to rheumatology and diagnosed with immune-mediated myositis due to immune checkpoint inhibitors were collected. A descriptive analysis was performed. <h3>Results</h3> Five patients were analyzed, 60% male, with a mean age of 65.8 years (56-78 years). The types of cancer were: melanoma (n=2), gastroesophageal junction cancer (n=1), cavum cancer (n=1) and pancreatic cancer (n=1); all in advanced stages with lymph node and/or metastatic involvement. The immunotherapy employed was: Nivolumab (PD-1 inhibitor) in three patients, Pembrolizumab (PD-1 inhibitor) in one patient and Darvalumab (PD-L1 inhibitor) in one patient; all at standard doses. Mean time from onset of symptoms was 4 months from drug initiation (1-10 months). In all 5 cases, the drug was discontinued with the onset of clinical symptoms and oral prednisone was prescribed at a dose between 10 and 20 mg per day. The symptom present in all patients was pain and weakness of proximal limbs (100%). In addition, one patient had ankle arthritis and another had dermatomyositis with typical cutaneous involvement (heliotrope erythema, V sign). In 3 patients there was an elevation of CK levels that resolved one month after discontinuation of the drug. Also, 3 patients, developed myositis-specific antibodies (AntiPM75 and Anti MI2, anti-PL7 and anti-TIF1gamma) that disappeared with drug withdrawal. One patient had anti-Ro52 and Ro60 antibodies that remain positive. Two patients underwent muscle MRI: one showed fatty infiltration in the gluteal musculature and atrophy with fatty infiltration in the right rectus femoris (image); in the other patient, signs of inflammatory myositis in the bilateral adductor group and in the right gluteus medius and gluteus minimus and fibrosing myositis in the iliac muscle was described. In both cases, the signs of myositis had disappeared in the control PET scan 5 months after drug discontinuation. In 4 patients, symptoms subsided in less than one month. One patient required the association of methotrexate to achieve corticosteroid withdrawal. <h3>Conclusion</h3> In our hospital, a total of 5 patients undergoing oncological treatment with immune checkpoint inhibitors have developed, in a mean time of 4 months from the start of the drug, a myopathy associated in 60% with the appearance of myositis-specific antibodies. This represents 1.8% of the total number of patients treated with these three drugs in our hospital. Withdrawal of the drug and treatment with prednisone at intermediate doses allowed clinical remission and normalization of laboratory and imaging tests. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.